JP6931367B2 - An optical communication system, an equalizer of the optical communication system, a connecting device and a receiving device, and a determination device, a determination method and a program of the amount of attenuation given by the equalization device. - Google Patents

Description

The present invention relates to an equalization technique in an optical communication system that transmits a plurality of wavelength division multiplexing optical signals using a spatial multiplexing optical fiber.

In order to increase the communication capacity, an optical communication system using a spatial multiplex optical fiber (hereinafter, also simply referred to as an optical communication system) is used. A multi-core optical fiber in which a plurality of cores are provided in one optical fiber is an example of a spatial multiplex optical fiber. A multimode optical fiber that transmits a plurality of propagation mode optical signals with one core is an example of a spatial multiplex optical fiber.

Patent Document 1 discloses a gain corrector for reducing the difference in optical power of each optical signal of a plurality of wavelength division multiplexing signals transmitted by a multi-core optical fiber. FIG. 1 is a schematic view of the gain corrector described in Patent Document 1. The multi-core optical fiber 91 and the multi-core optical fiber 97 each have a total of N cores from the first to the Nth (N is an integer of 2 or more). Each of the N cores transmits a wavelength division multiplexing optical signal. The fan-out unit 92 separates the N wavelength division multiplexing optical signals transmitted by the multi-core optical fiber 91, and outputs the wavelength division multiplexing optical signals to each of the N single core optical fibers 93-1 to 93-N. For example, the wavelength division multiplexing optical signal of the nth core (n is an integer from 1 to N) of the multi-core optical fiber 91 is output to the single-core optical fiber 93-n. The equalization unit 94-n adjusts the optical power of the optical signal of each wavelength of the wavelength division multiplexing optical signal transmitted by the single-core optical fiber 93-n, and outputs the optical power to the single-core optical fiber 95-n. The fan-in unit 96 outputs a wavelength division multiplexing optical signal transmitted by each of the single-core optical fibers 95-1 to 95-N to the corresponding core of the multi-core optical fiber 97. For example, the fan-in unit 96 outputs a wavelength division multiplexing optical signal transmitted by the single-core optical fiber 95-n to the nth core of the multi-core optical fiber 97.

Japanese Unexamined Patent Publication No. 2016-219753

The configuration of Patent Document 1 is a fan-out section 92 and a fan-in section 96 for separating and multiplexing each wavelength-multiplexed optical signal transmitted by a space-multiplexed optical fiber, and a wavelength-division-multiplexed optical signal transmitted by a space-multiplexed optical fiber. Since the same number of equalizing units 94-1 to 94-N as the number of the above is required, the cost is high.

The present invention provides a technique for equalizing a plurality of wavelength division multiplexing optical signals transmitted by a spatial multiplexing optical fiber at low cost.

According to one aspect of the present invention, N × M pieces of light are obtained by spatially multiplexing N wavelength-multiplexed signals obtained by wavelength-multiplexing optical signals of the first to Mth wavelengths (M is an integer of 2 or more). The determination method in the determination device for determining the amount of attenuation given to the optical signal of the first wavelength to the M wavelength in the equalizer of the optical communication system for transmitting the signal is the N × M input to the equalizer. The first optical power, which is the minimum optical power among the optical powers of the optical signals, is determined, and the N elements input to the equalizer for each of the first wavelength to the M wavelength. The second optical power is based on the determination of the maximum value of the difference in optical power of the optical signal and the sum of the maximum value of the maximum value determined for each of the first wavelength to the M wavelength and the first optical power. And the difference between the maximum value of the optical power of the N optical signals of the mth wavelength (m is an integer from 1 to M) and the second optical power input to the equalizer. It is characterized by including determining the amount of attenuation of the mth wavelength based on the above.

According to the present invention, it is possible to equalize a plurality of wavelength division multiplexing optical signals transmitted by a spatial multiplexing optical fiber at low cost.

The block diagram of the gain corrector by the background technology. The block diagram of the optical communication system by one Embodiment. The block diagram of the equalization device by one Embodiment. The figure which shows the optical power of the optical channel of each input optical signal, the amount of attenuation given by the equalizing part, and the optical power of the optical channel of each optical signal after attenuation. The flowchart of the determination process of the attenuation amount of each channel executed by the determination apparatus by one Embodiment. The figure which shows the attenuation amount determined by the determination apparatus by one Embodiment, and the optical power of the optical channel of each optical signal after attenuation.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. The following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more of the plurality of features described in the embodiments may be arbitrarily combined. In addition, the same or similar configuration will be given the same reference number, and duplicated explanations will be omitted.

<First Embodiment>
FIG. 2 is a configuration diagram of an optical communication system using a multi-core optical fiber according to the present embodiment. The transmitting device 1 communicates with the receiving device 2 via the optical transmission line 4. The optical transmission line 4 includes a multi-core optical fiber and an optical repeater (not shown) having an optical amplifier that amplifies a wavelength division multiplexing optical signal transmitted in each core of the multi-core optical fiber. Further, the optical communication system includes one or more connecting devices 3. Although the optical communication system of FIG. 2 is provided with three connecting devices 3, it is an example, and the number of connecting devices 3 can be any one or more. The connecting device 3 has an equalizing device according to the present embodiment.

FIG. 3 is a block diagram of the equalization device according to the present embodiment. The equalizing device has an equalizing unit 30. The equalizing unit 30 gives attenuation having a predetermined wavelength characteristic to the wavelength division multiplexing optical signal transmitted by each of the N (N is an integer of 2 or more) cores of the multi-core optical fiber 41 on the input side, and the multi-core on the output side. Output to the corresponding core of the N cores of the optical fiber 42. In the following description, the wavelength division multiplexing optical signal transmitted by the nth core (n is an integer from 1 to N) of the multi-core optical fiber 41 and the multi-core optical fiber 42 is referred to as an optical signal #n. Further, in each wavelength division multiplexing optical signal, it is assumed that M (M is an integer of 2 or more) optical signals are wavelength-multiplexed. Then, each of the M optical signals constituting one wavelength division multiplexing optical signal is referred to as a channel. Further, the m-th (m is an integer from 1 to M) optical signal of one wavelength division multiplexing optical signal is referred to as CH # m. In addition, m is also an index indicating a wavelength, and in each wavelength division multiplexing optical signal, a channel having the same value of m means that the wavelength is the same.

The equalizing unit 30 can give a different amount of attenuation depending on the wavelength. That is, the equalizing unit 30 can give a different amount of attenuation for each channel. However, the equalizing unit 30 can give only the same amount of attenuation for the optical signals # 1 to the optical signal # N for the same channel.

For example, it is assumed that N = 2 and M = 3, and the optical power of each channel of the optical signal input to the equalization unit 30 is as shown in FIG. 4 (A). In an optical communication system, it is required to reduce the difference in optical power between the optical signals of each channel of each wavelength division multiplexing signal. For example, in order to reduce the difference in optical power of each channel of the optical signal # 1, as shown in FIG. 4B, if CH # 1 is attenuated by 1 dB, CH # 2 is attenuated by 0 dB, and CH3 is attenuated by 5 dB. good. In this case, the optical power of each channel of the optical signal # 1 after attenuation is 2 dBm in total, as shown in FIG. 4 (B). However, in this case, the optical power of each channel of the attenuated optical signal # 2 is 5 dBm for CH # 1, 4 dBm for CH # 2, and 1 dBm for CH # 3, as shown in FIG. 4 (B).

As shown in FIG. 4A, the maximum value of the difference in the optical power of each channel of the optical signal # 1 and the optical signal # 2 is CH # 3 of the optical signal # 1 and CH # 2 of the optical signal # 1. The difference is 5 dB. On the other hand, as shown in FIG. 4B, the maximum value of the difference in the optical power of each channel of the attenuated optical signal # 1 and the optical signal # 2 is the CH # 1 and the optical signal # 2 of the optical signal # 2. It is 4 dB, which is the difference from CH # 3, and is improved by only 1 dB as compared with that before attenuation. Further, as shown in FIG. 4A, the minimum value of the optical power of each channel of the optical signal # 1 and the optical signal # 2 is 2 dBm of CH # 2 of the optical signal # 1. On the other hand, as shown in FIG. 4 (B), the minimum value of the optical power of each channel of the optical signal # 1 and the optical signal # 2 after attenuation is 1 dBm of CH # 3 of the optical signal # 2, and is before attenuation. Compared with, it is deteriorated by 1 dB.

On the other hand, FIG. 4C shows a case where the difference in optical power of each channel of the optical signal # 2 is reduced, and CH # 1 is attenuated by 2 dB, CH # 2 is attenuated by 0 dB, and CH3 is attenuated by 2 dB. In this case, as shown in FIG. 4C, the optical power of each channel of the attenuated optical signal # 2 is 4 dBm in total, and the optical power of each channel of the attenuated optical signal # 1 is FIG. As shown in (C), CH # 1 is 1 dBm, CH # 2 is 2 dBm, and CH # 3 is 5 dBm.

As shown in FIG. 4C, the maximum value of the difference in optical power between each channel of the attenuated optical signal # 1 and optical signal # 2 is the CH # 1 of the optical signal # 1 and the CH of the optical signal # 1. It is 4 dB, which is the difference from # 3, and is improved by only 1 dB compared to before attenuation. Further, as shown in FIG. 4C, the minimum value of the optical power of each channel of the optical signal # 1 and the optical signal # 2 after attenuation is 1 dBm of CH # 1 of the optical signal # 1 and before attenuation. Compared with, it is deteriorated by 1 dB.

The equalizing unit 30 of the equalizing device included in the connecting device 3 in the present embodiment does not deteriorate the minimum value of the optical power of each channel of each optical signal before and after attenuation, and each of the optical signals. Minimize the maximum difference in optical power between channels as much as possible.

FIG. 5 is a flowchart of a determination process for determining the attenuation amount of each channel given by the equalization unit 30 of the equalizer according to the present embodiment. The process of FIG. 5 is executed by the determination device of the present embodiment. For each of the optical signals # 1 to #N, the determination device has a value indicating the optical power of M channels, that is, a value indicating a total of N × M optical powers, together with information for identifying the optical signal and the channel. Entered. The information for specifying the optical signal is n (integer from 1 to N), and the information for specifying the channel is m (integer from 1 to M). The determination device outputs the attenuation amount of each of the M channels based on the input value indicating the total N × M optical powers.

First, in S10, the determination device determines the minimum optical power Pmin out of N × M optical powers. For example, when a total of six optical powers shown in FIG. 4A are input, 2 dBm of CH # 2 of the optical signal # 1 becomes Pmin. In S11, the determination device obtains the maximum value of the difference in optical power between the optical signal # 1 to the optical signal # N for each channel, and further determines the maximum value as ΔPmax. For example, when a total of six optical powers shown in FIG. 4A are input, the maximum value of the difference of CH # 1 is 3 dB, the maximum value of the difference of CH # 2 is 2 dB, and CH # 3 The maximum value of the difference is 1 dB. In the example of FIG. 4A, since N = 2, the difference between the optical signal # 1 and the optical signal # 2 is the maximum value of the difference between the optical signals of the same channel, but generally. for each channel, a demand difference of the _{two N} C is the maximum value, the maximum value of the difference of the optical power of the optical signal of the channel. In the example of FIG. 4A, the maximum value of the difference of CH # 1 is 3 dB, the maximum value of the difference of CH # 2 is 2 dB, and the maximum value of the difference of CH # 3 is 1 dB. ΔPmax is 3 dB, which is the maximum value thereof.

In S12, the determination device determines Pmax as Pmin + ΔPmax. In this example, Pmin = 2 dBm and ΔPmax = 3 dB, so Pmax = 5 dBm. The determination device initializes the value m indicating the channel number to 1 in S13, and obtains the attenuation amount of CH # m by Pm_max-Pmax in S14. When Pm_max-Pmax has a negative value, the attenuation amount of CH # m is set to 0. Here, Pm_max is the maximum value of the optical power of CH # m of each of the optical signals # 1 to # N. In the example of FIG. 4A, P1_max = 6 dBm, P2_max = 4 dBm, and P3_max = 7 dBm. Therefore, in the first processing of S14, the attenuation amount of CH # 1 is determined to be 6 dBm-5 dBm = 1 dB. The determination device determines in S15 whether m = M, and if it is not m = M, increases m by 1 in S16, and repeats the process from S14 until m = M in S15. Therefore, in the next processing of S14, the attenuation amount of CH # 2 is determined to be 0 dB because 4 dBm-5 dBm is a negative value. Further, in the next processing of S14, the attenuation amount of CH # 3 is determined to be 7 dBm-5 dBm = 2 dB.

FIG. 6 shows the above-mentioned attenuation amount output by the determination device when a total of six optical powers shown in FIG. 4A are input to the determination device, that is, CH # 1, CH # 2, and CH # 3, respectively. It shows the optical power of each channel of the optical signal # 1 and the optical signal # 2 after attenuation when the amount of attenuation is 1 dB, 0 dB, and 2 dB. As shown in FIG. 6, the minimum value of the optical power of each channel of the optical signal # 1 and the optical signal # 2 after attenuation is 2 dBm of CH # 1 and CH # 2 of the optical signal # 1, and the maximum value is , CH # 3 of the optical signal # 1 and 5 dBm of CH # 1 of the optical signal # 2. Therefore, the maximum value of the difference in optical power between each channel of the optical signal # 1 and the optical signal # 2 after attenuation is 3 dB, which is improved by 2 dB as compared with that before attenuation, and FIGS. 4 (B) and 4 (C). ), It is improved by 1 dB. Further, the minimum value of the optical power of each channel of the optical signal # 1 and the optical signal # 2 after attenuation is 2 dBm, which is not deteriorated as compared with that before attenuation.

Subsequently, the concept of the processing of FIG. 5 will be described. Since the equalizer according to the present embodiment can give the same amount of attenuation to the same channel of each optical signal, the maximum value of the difference in optical power of each channel cannot be reduced. That is, in the case of FIG. 4A, the maximum value of the difference of CH # 1 is 3 dB, the maximum value of the difference of CH # 2 is 2 dB, and the maximum value of the difference of CH # 3 is 1 dB. This maximum value cannot be reduced. Therefore, the difference between the minimum optical power and the maximum optical power in all channels of the attenuated optical signals # 1 to # N is 3 dB, which is the maximum value among these three maximum values, that is, S11. It cannot be smaller than the desired ΔPmax. Further, in order to prevent deterioration of the optical signal, the minimum optical power among all channels of the attenuated optical signals # 1 to #N must be Pmin or more obtained in S10. Therefore, if the optical power of each channel of the attenuated optical signals # 1 to # N is Pmin or more and Pmax = Pmin + ΔPmax or less, the difference in the optical power of each channel of the attenuated optical signal becomes the minimum. Moreover, the minimum value of the optical power of each channel of each optical signal after attenuation is not deteriorated as compared with that before attenuation.

Here, the attenuation amount of each channel should be small, so that the difference between the maximum values Pm_max and Pmax of the optical power of each channel is obtained and used as the attenuation amount. With this configuration, the minimum value of the optical power of each channel of each optical signal is not deteriorated before and after attenuation, and the maximum value of the difference in optical power of each channel of each optical signal is made as small as possible. be able to. More specifically, the minimum value of the optical power of each channel of each attenuated optical signal is the same as that before attenuation, and the maximum value of the difference in optical power of each channel of each attenuated optical signal is ΔPmax. Can be done.

As described above, the equalization device in the present embodiment does not require the fan-out section and the fine-in section and the equalization section having the same number of spatial multiplexings, and can be used for a plurality of wavelength division multiplexing optical signals transmitted by the spatial multiplexing optical fiber. Equalization can be performed at low cost.

The determination device of the present embodiment includes a first determination unit, a second determination unit, a third determination unit, and a determination unit. Further, the determination device includes the optical power of a total of N × M optical signals included in the N wavelength division multiplexing optical signals, each of which has optical signals of the first wavelength to the Mth wavelength, which are input to the equalizer. A value indicating is entered. The first determination unit determines the first optical power (Pmin), which is the minimum optical power among the optical powers of N × M optical signals. The second determination unit determines the maximum value of the difference in optical power of N optical signals for each of the first wavelength to the Mth wavelength. The third determination unit determines the second optical power (Pmax) based on the sum of the maximum value (ΔPmax) of the maximum value determined for each of the first to M wavelengths and the first optical power. The determination unit determines the amount of attenuation of the mth wavelength based on the difference between the maximum value of the optical power of N optical signals of the mth wavelength (m is an integer from 1 to M) and the second optical power.

In the present embodiment, the optical transmission line 4 has an optical repeater that performs optical amplification, and the connecting device 3 has only an equalizing device having an equalizing unit 30. However, it is also possible to provide an optical amplifier for optical amplification on the upstream side or the downstream side of the equalizing device and configure the connecting device 3 as an optical repeater. Further, the equalizing device of the present embodiment can be provided in the receiving device 2.

Further, in the present embodiment, the optical communication system is a multi-core optical fiber having N cores, but a multi-mode optical fiber that transmits N wavelength division multiplexing optical signals in each of N different propagation modes. The present invention can also be applied to.

The determination device according to the present invention can be realized by a program that operates the computer as the determination device. These computer programs are stored in a computer-readable storage medium or can be distributed over a network.

The invention is not limited to the above-described embodiment, and various modifications and changes can be made within the scope of the gist of the invention.

1: Transmitter, 2: Receiver, 3: Connection, 30: Equalizer

Claims (11)

An optical communication system that transmits N × M optical signals by spatially multiplexing N wavelength division multiplexing signals that are wavelength-multiplexed optical signals of the first to M wavelengths (M is an integer of 2 or more). It is a determination method in a determination device that determines the amount of attenuation given to an optical signal of the first wavelength to the M wavelength in an equalizer.
Determining the first optical power, which is the minimum optical power among the optical powers of the N × M optical signals input to the equalizing device,
For each of the first wavelength to the M wavelength, the maximum value of the difference in optical power of the N optical signals input to the equalizer is determined.
The second optical power is determined based on the sum of the maximum value of the maximum value determined for each of the first wavelength to the M wavelength and the first optical power.
Based on the difference between the maximum value of the optical power of the N optical signals of the mth wavelength (m is an integer from 1 to M) input to the equalizer and the second optical power, the mth wavelength Determining the amount of attenuation and
A determination method characterized by including. When the value obtained by subtracting the second optical power from the maximum value of the optical power of the N optical signals of the mth wavelength input to the equalizing apparatus is 0 or more, the determination device has the m. The amount of wavelength attenuation is determined by the difference between the maximum value of the optical power of the N optical signals of the mth wavelength input to the equalizer and the second optical power, and is input to the equalizer. When the value obtained by subtracting the second optical power from the maximum value of the optical powers of the N optical signals of the mth wavelength is negative, the attenuation amount of the mth wavelength is determined to be 0. The determination method according to claim 1. An optical communication system that transmits N × M optical signals by spatially multiplexing N wavelength division multiplexing signals that are wavelength-multiplexed optical signals of the first to M wavelengths (M is an integer of 2 or more). A determinant that determines the amount of attenuation given to an optical signal from the first wavelength to the M wavelength in an equalizer.
A first determination means for determining the first optical power, which is the minimum optical power among the optical powers of the N × M optical signals input to the equalizer.
A second determination means for determining the maximum value of the difference in optical power of the N optical signals input to the equalizer for each of the first wavelength to the M wavelength.
A third determination means for determining the second optical power based on the sum of the maximum value of the maximum value determined for each of the first wavelength to the M wavelength and the first optical power.
Based on the difference between the maximum value of the optical power of the N optical signals of the mth wavelength (m is an integer from 1 to M) input to the equalizer and the second optical power, the mth wavelength Determining means for determining the amount of attenuation and
A determination device characterized by being equipped with. When the third determination means has a value obtained by subtracting the second optical power from the maximum value of the optical power of the N optical signals of the m wavelength input to the equalizer, the value is 0 or more. The amount of attenuation of the mth wavelength is determined by the difference between the maximum value of the optical power of the N optical signals of the mth wavelength input to the equalizer and the second optical power, and the equalizer is used. When the value obtained by subtracting the second optical power from the maximum value of the optical power of the N optical signals of the mth wavelength input to is negative, the attenuation amount of the m wavelength is determined to be 0. 3. The determination device according to claim 3. A program comprising operating a computer as the determination device according to claim 3 or 4. In an optical communication system that transmits N × M optical signals by spatially multiplexing N wavelength division multiplexing signals that are wavelength-multiplexed optical signals of the first to M wavelengths (M is an integer of 2 or more). The equalizer used
It has an equalization means for giving an attenuation of a predetermined amount of attenuation to an optical signal of each wavelength of the N wavelength division multiplexing signals input to the equalizer and outputting the signal.
The amount of attenuation of the mth wavelength (m is an integer from 1 to M) given by the equalizing means is the maximum value of the optical power of the N optical signals of the mth wavelength input to the equalizing device. When it is larger than the first optical power, it is the difference between the maximum value of the optical power of the N optical signals of the mth wavelength input to the equalizing device and the first optical power, and the equalizing device. When the maximum value of the optical power of the N optical signals of the mth wavelength to be input is equal to or less than the first optical power, it is 0.
The first optical power is the sum of the first optical power difference and the second optical power.
The second optical power is the minimum optical power among the optical powers of the N × M optical signals input to the equalizer.
The first optical power difference is the maximum value of the second optical power difference between the first wavelength and the M wavelength.
The second optical power difference of the mth wavelength is the maximum value of the difference in the optical powers of the N optical signals of the mth wavelength input to the equalizer. In an optical communication system that transmits N × M optical signals by spatially multiplexing N wavelength division multiplexing signals that are wavelength-multiplexed optical signals of the first to M wavelengths (M is an integer of 2 or more). , A connecting device for connecting a first space multiplex optical fiber and a second space multiplex optical fiber.
The connecting device includes the equalizing device according to claim 6. An optical communication system that transmits N × M optical signals by spatially multiplexing N wavelength division multiplexing signals that are wavelength-multiplexed optical signals of the first to M wavelengths (M is an integer of 2 or more). It is a receiving device
The receiving device includes the equalizing device according to claim 6. By using a space-multiplexed optical fiber, N × M light can be obtained by spatially multiplexing N wavelength-multiplexed signals obtained by wavelength-multiplexing optical signals of the first to M wavelengths (M is an integer of 2 or more). An optical communication system that transmits signals
The optical communication system includes the equalization device according to claim 6. The optical communication system according to claim 9, wherein the spatial multiplexing optical fiber is a multi-core optical fiber. The optical communication system according to claim 9, wherein the spatial multiplexing optical fiber is a multimode optical fiber.

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